Retrieve current location when application is in background - ios

Question

I've built an application where you can press a start button. Once the button is pressed the application will get user location every 10 second all the way till the stop button is pressed. When I leave the application or if the screen gets black, it will NOT get any more locations till I re-enter the application.
So, I'm currently trying to update the locations when the application is minimized. (I guess it's called in the background?), and also when the screen turns black. But my questions is:
Should I write this code in the AppDelegate?, if so. How can I know
if the button was pressed or not?
Where exactly in the AppDelegate should I add the code? And how can
I pass the locations back to the correct ViewController? (Since I
cannot make any prepare for segue from AppDelegate)
If you know the answers of this questions, please do not hesitate to answer them. :) I would really appreciate it!

Answer 1

The best way to get user's location in background is to use the Significant-Change Location Service according to apple's documentation put this func in your class:
func startReceivingSignificantLocationChanges() {
let authorizationStatus = CLLocationManager.authorizationStatus()
if authorizationStatus != .authorizedAlways {
// User has not authorized access to location information.
return
}
if !CLLocationManager.significantLocationChangeMonitoringAvailable() {
// The service is not available.
return
}
locationManager.delegate = self
locationManager.startMonitoringSignificantLocationChanges()
}
and also this func:
func locationManager(_ manager: CLLocationManager, didUpdateLocations
locations: [CLLocation]) {
let lastLocation = locations.last!
// Do something with the location.
}
so you just need to call startReceivingSignificantLocationChanges() inside your button and it will call locationManager(_ manager: CLLocationManager,didUpdateLocations locations: [CLLocation]), so do what you want with the location there.
Remember to ask permission to use location and to stop tracking with locationManager.stopMonitoringSignificantLocationChanges()

Answer 2

Take location permission for Always Allow
Set location manager for allowsBackgroundLocationUpdates true
from the above way you can get location in every location changes store this information and it send to server. Below is the sample code
typealias LocateMeCallback = (_ location: CLLocation?) -> Void
/*
LocationTracker to track the user in while navigating from one place to other and store new locations in locations array.
**/
class LocationTracker: NSObject {
static let shared = LocationTracker()
var lastLocation: CLLocation?
var locations: [CLLocation] = []
var previousLocation: CLLocation?
var isPreviousIsSameAsCurrent: Bool {
if let previous = previousLocation, let last = lastLocation {
return previous == last
}
return false
}
var isAggressiveModeOn = false
var locationManager: CLLocationManager = {
let locationManager = CLLocationManager()
locationManager.allowsBackgroundLocationUpdates = true
locationManager.pausesLocationUpdatesAutomatically = true
locationManager.activityType = .automotiveNavigation
return locationManager
}()
var locateMeCallback: LocateMeCallback?
var isCurrentLocationAvailable: Bool {
if lastLocation != nil {
return true
}
return false
}
func enableLocationServices() {
locationManager.delegate = self
switch CLLocationManager.authorizationStatus() {
case .notDetermined:
// Request when-in-use authorization initially
locationManager.requestWhenInUseAuthorization()
case .restricted, .denied:
// Disable location features
print("Fail permission to get current location of user")
case .authorizedWhenInUse:
// Enable basic location features
enableMyWhenInUseFeatures()
case .authorizedAlways:
// Enable any of your app's location features
enableMyAlwaysFeatures()
}
}
func enableMyWhenInUseFeatures() {
locationManager.startUpdatingLocation()
locationManager.delegate = self
escalateLocationServiceAuthorization()
}
func escalateLocationServiceAuthorization() {
// Escalate only when the authorization is set to when-in-use
if CLLocationManager.authorizationStatus() == .authorizedWhenInUse {
locationManager.requestAlwaysAuthorization()
}
}
func enableMyAlwaysFeatures() {
enableCoarseLocationFetch()
locationManager.startUpdatingLocation()
locationManager.delegate = self
}
// Enable Rough Location Fetch
func enableCoarseLocationFetch() {
isAggressiveModeOn = false
locationManager.desiredAccuracy = kCLLocationAccuracyKilometer
locationManager.distanceFilter = 100
}
// Enable Aggressive Location Fetch
func enableAggressiveLocationFetch() {
isAggressiveModeOn = true
locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
locationManager.distanceFilter = 10
}
func locateMe(callback: #escaping LocateMeCallback) {
self.locateMeCallback = callback
if lastLocation == nil {
enableLocationServices()
} else {
callback(lastLocation)
}
}
func startTracking() {
enableLocationServices()
}
func stopTracking() {
locationManager.stopUpdatingLocation()
}
func resetPreviousLocation() {
previousLocation = nil
}
private override init() {}
}
extension LocationTracker: CLLocationManagerDelegate {
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
print(locations)
guard let location = locations.first else { return }
guard -location.timestamp.timeIntervalSinceNow < 120, // Validate only location fetched recently
location.horizontalAccuracy > 0, // Validate Horizontal Accuracy - Ve means Invalid
location.horizontalAccuracy < 200 // Validate Horizontal Accuracy > 100 M
else {
print("invalid location received OR ignore old (cached) updates")
return
}
self.locations.append(location)
lastLocation = location
if let activeRide = RideManager.shared.activeRide,
let _ = AccessTokenHelper.shared.accessToken,
let activeRideId = activeRide.ride_id,
let type = activeRide.rideStatusTypeOptional,
type == .started {
//Store Location For A particular Ride after Start
LocationUpdater.shared.saveInDataBase(rideId: activeRideId, locations: [location])
}
}
func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
print(error.localizedDescription)
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
enableLocationServices()
}
}
/*
This class having responsibility of Updating the location on server after n second and update path after n second.
**/
class LocationTimer {
static let time: Double = 30
}
/*
class to update locations to server after nth second
**/
class LocationUpdater: NSObject {
static let shared = LocationUpdater(n: Double(LocationTimer.time), tracker: LocationTracker.shared)
let n: Double
private let tracker: LocationTracker
var timer: Timer! = nil
init(n: Double, tracker: LocationTracker) {
self.n = n
self.tracker = tracker
super.init()
}
func startUpdater() {
self.timer?.invalidate()
self.timer = nil
self.timer = Timer.scheduledTimer(timeInterval: n, target: self, selector: #selector(updateLocationsToServer), userInfo: nil, repeats: true)
self.timer.fire()
}
func stopUpdater() {
self.timer?.invalidate()
self.timer = nil
}
#objc func updateLocationsToServer() {
// update to server
}
}
// usage
LocationTracker.shared.startTracking()
LocationUpdater.shared.startUpdater()